1 files changed, 127 insertions, 0 deletions
diff --git a/toolkit/components/utils/test/unit/test_Sampling.js b/toolkit/components/utils/test/unit/test_Sampling.js
new file mode 100644
index 0000000000..c698ddf8b1
--- /dev/null
+++ b/toolkit/components/utils/test/unit/test_Sampling.js
@@ -0,0 +1,127 @@
+"use strict";
+
+const { Sampling } = ChromeUtils.importESModule(
+  "resource://gre/modules/components-utils/Sampling.sys.mjs"
+);
+
+add_task(async function testStableSample() {
+  // Absolute samples
+  equal(
+    await Sampling.stableSample("test", 1),
+    true,
+    "stableSample returns true for 100% sample"
+  );
+  equal(
+    await Sampling.stableSample("test", 0),
+    false,
+    "stableSample returns false for 0% sample"
+  );
+
+  // Known samples. The numbers are nonces to make the tests pass
+  equal(
+    await Sampling.stableSample("test-0", 0.5),
+    true,
+    "stableSample returns true for known matching sample"
+  );
+  equal(
+    await Sampling.stableSample("test-1", 0.5),
+    false,
+    "stableSample returns false for known non-matching sample"
+  );
+});
+
+add_task(async function testBucketSample() {
+  // Absolute samples
+  equal(
+    await Sampling.bucketSample("test", 0, 10, 10),
+    true,
+    "bucketSample returns true for 100% sample"
+  );
+  equal(
+    await Sampling.bucketSample("test", 0, 0, 10),
+    false,
+    "bucketSample returns false for 0% sample"
+  );
+
+  // Known samples. The numbers are nonces to make the tests pass
+  equal(
+    await Sampling.bucketSample("test-0", 0, 5, 10),
+    true,
+    "bucketSample returns true for known matching sample"
+  );
+  equal(
+    await Sampling.bucketSample("test-1", 0, 5, 10),
+    false,
+    "bucketSample returns false for known non-matching sample"
+  );
+});
+
+add_task(async function testRatioSample() {
+  // Invalid input
+  await Assert.rejects(
+    Sampling.ratioSample("test", []),
+    /ratios must be at least 1 element long/,
+    "ratioSample rejects for a list with no ratios"
+  );
+
+  // Absolute samples
+  equal(
+    await Sampling.ratioSample("test", [1]),
+    0,
+    "ratioSample returns 0 for a list with only 1 ratio"
+  );
+  equal(
+    await Sampling.ratioSample("test", [0, 0, 1, 0]),
+    2,
+    "ratioSample returns the only non-zero bucket if all other buckets are zero"
+  );
+
+  // Known samples. The numbers are nonces to make the tests pass
+  equal(
+    await Sampling.ratioSample("test-0", [1, 1]),
+    0,
+    "ratioSample returns the correct index for known matching sample"
+  );
+  equal(
+    await Sampling.ratioSample("test-1", [1, 1]),
+    1,
+    "ratioSample returns the correct index for known non-matching sample"
+  );
+});
+
+add_task(async function testFractionToKey() {
+  // Test that results are always 12 character hexadecimal strings.
+  const expected_regex = /[0-9a-f]{12}/;
+  const count = 100;
+  let successes = 0;
+  for (let i = 0; i < count; i++) {
+    const p = Sampling.fractionToKey(Math.random());
+    if (expected_regex.test(p)) {
+      successes++;
+    }
+  }
+  equal(successes, count, "fractionToKey makes keys the right length");
+});
+
+add_task(async function testTruncatedHash() {
+  const expected_regex = /[0-9a-f]{12}/;
+  const count = 100;
+  let successes = 0;
+  for (let i = 0; i < count; i++) {
+    const h = await Sampling.truncatedHash(Math.random());
+    if (expected_regex.test(h)) {
+      successes++;
+    }
+  }
+  equal(successes, count, "truncatedHash makes hashes the right length");
+});
+
+add_task(async function testBufferToHex() {
+  const data = new ArrayBuffer(4);
+  const view = new DataView(data);
+  view.setUint8(0, 0xff);
+  view.setUint8(1, 0x7f);
+  view.setUint8(2, 0x3f);
+  view.setUint8(3, 0x1f);
+  equal(Sampling.bufferToHex(data), "ff7f3f1f");
+});